When I run stack upload I get an error:
Environment variable GPG_TTY is not set (see man gpg-agent)
Unable to find gpg2 or gpg executable
The upload appears to succeed, but the error concerns me.
What are the consequences of this error? Is there a way to avoid to suppress it?
As per discussion in the comments the errors are due to stack trying to automatically GPG sign packages that are being uploaded as of version 1.1.0.
To my understanding this is a stack-specific feature (with no package signing built into cabal or hackage), and it can be disabled with --no-signature command line option to stack upload.
来源：https://stackoverflow.com/questions/41415900/gpg-error-when-using-stack-upload